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| <h1 class="c1"><a href="../index.html">Boost.Python</a></h1> |
| |
| <h2 class="c2">Header <boost/python/type_id.hpp></h2> |
| </table> |
| <hr> |
| |
| <h2>Contents</h2> |
| |
| <dl class="page-index"> |
| <dt><a href="#introduction">Introduction</a></dt> |
| |
| <dt><a href="#classes">Classes</a></dt> |
| |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#type_info-spec">Class <code>type_info</code></a></dt> |
| |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#type_info-spec-synopsis">Class |
| <code>type_info</code> synopsis</a></dt> |
| |
| <dt><a href="#type_infospec-ctors">Class <code>type_info</code> |
| constructor</a></dt> |
| |
| <dt><a href="#type_infospec-comparisons">Class |
| <code>type_info</code> comparison functions</a></dt> |
| |
| <dt><a href="#type_infospec-observers">Class |
| <code>type_info</code> observer functions</a></dt> |
| </dl> |
| </dd> |
| </dl> |
| </dd> |
| |
| <dt><a href="#functions">Functions</a></dt> |
| |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#type_id-spec">type_id</a></dt> |
| </dl> |
| </dd> |
| |
| <dt><a href="#examples">Example</a></dt> |
| </dl> |
| <hr> |
| |
| <h2><a name="introduction"></a>Introduction</h2> |
| |
| <p><code><boost/python/type_id.hpp></code> provides types and |
| functions for runtime type identification like those of of |
| <code><typeinfo></code>. It exists mostly to work around certain |
| compiler bugs and platform-dependent interactions with shared |
| libraries.</p> |
| |
| <h2><a name="classes"></a>Classes</h2> |
| |
| <h3><a name="type_info-spec"></a>Class <code>type_info</code></h3> |
| |
| <p><code>type_info</code> instances identify a type. As |
| <code>std::type_info</code> is specified to (but unlike its |
| implementation in some compilers), <code>boost::python::type_info</code> |
| never represents top-level references or cv-qualification (see section |
| 5.2.8 in the C++ standard). Unlike <code>std::type_info</code>, |
| <code>boost::python::type_info</code> instances are copyable, and |
| comparisons always work reliably across shared library boundaries.</p> |
| |
| <h4><a name="type_info-spec-synopsis"></a>Class type_info synopsis</h4> |
| <pre> |
| namespace boost { namespace python |
| { |
| class type_info : <a href= |
| "../../../utility/operators.htm#totally_ordered1">totally_ordered</a><type_info> |
| { |
| public: |
| // constructor |
| type_info(std::type_info const& = typeid(void)); |
| |
| // comparisons |
| bool operator<(type_info const& rhs) const; |
| bool operator==(type_info const& rhs) const; |
| |
| // observers |
| char const* name() const; |
| }; |
| }} |
| </pre> |
| |
| <h4><a name="type_infospec-ctors">Class <code>type_info</code> |
| constructor</a></h4> |
| <pre> |
| type_info(std::type_info const& = typeid(void)); |
| </pre> |
| |
| <dl class="function-semantics"> |
| <dt><b>Effects:</b> constructs a <code>type_info</code> object which |
| identifies the same type as its argument.</dt> |
| |
| <dt><b>Rationale:</b> Since it is occasionally necessary to make an |
| array of <code>type_info</code> objects a benign default argument is |
| supplied. <span class="c3"><b>Note:</b></span> this constructor does |
| <i>not</i> correct for non-conformance of compiler |
| <code>typeid()</code> implementations. See <code><a href= |
| "#type_id-spec">type_id</a></code>, below.</dt> |
| </dl> |
| |
| <h4><a name="type_infospec-comparisons">Class <code>type_info</code> |
| comparisons</a></h4> |
| <pre> |
| bool operator<(type_info const& rhs) const; |
| </pre> |
| |
| <dl class="function-semantics"> |
| <dt><b>Effects:</b> yields a total order over <code>type_info</code> |
| objects.</dt> |
| </dl> |
| <pre> |
| bool operator==(type_info const& rhs) const; |
| </pre> |
| |
| <dl class="function-semantics"> |
| <dt><b>Returns:</b> <code>true</code> iff the two values describe the |
| same type.</dt> |
| </dl> |
| |
| <dl class="function-semantics"> |
| <dt><b>Note:</b> The use of <code><a href= |
| "../../../utility/operators.htm#totally_ordered1">totally_ordered</a><type_info></code> |
| as a private base class supplies operators <code><=</code>, |
| <code>>=</code>, <code>></code>, and <code>!=</code></dt> |
| </dl> |
| |
| <h4><a name="type_infospec-observers">Class <code>type_info</code> |
| observers</a></h4> |
| <pre> |
| char const* name() const; |
| </pre> |
| |
| <dl class="function-semantics"> |
| <dt><b>Returns:</b> The result of calling <code>name()</code> on the |
| argument used to construct the object.</dt> |
| </dl> |
| |
| <h2><a name="functions"></a>Functions</h2> |
| <pre> |
| std::ostream& operator<<(std::ostream&s, type_info const&x); |
| </pre> |
| |
| <dl class="function-semantics"> |
| <dt><b>Effects:</b> Writes a description of the type described by to |
| <code>x</code> into <code>s</code>.</dt> |
| |
| <dt><b>Rationale:</b> Not every C++ implementation provides a truly |
| human-readable <code>type_info::name()</code> string, but for some we |
| may be able to decode the string and produce a reasonable |
| representation.</dt> |
| </dl> |
| <pre> |
| <a name="type_id-spec">template <class T> type_info type_id</a>() |
| </pre> |
| |
| <dl class="function-semantics"> |
| <dt><b>Returns:</b> <code>type_info(typeid(T))</code></dt> |
| |
| <dt><b>Note:</b> On some non-conforming C++ implementations, the code |
| is not actually as simple as described above; the semantics are |
| adjusted to work <i>as-if</i> the C++ implementation were |
| conforming.</dt> |
| </dl> |
| |
| <h2><a name="examples"></a>Example</h2> |
| The following example, though silly, illustrates how the |
| <code>type_id</code> facility might be used |
| <pre> |
| #include <boost/python/type_id.hpp> |
| |
| // Returns true iff the user passes an int argument |
| template <class T> |
| bool is_int(T x) |
| { |
| using boost::python::type_id; |
| return type_id<T>() == type_id<int>(); |
| } |
| </pre> |
| |
| <p>Revised |
| <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> |
| 13 November, 2002 |
| <!--webbot bot="Timestamp" endspan i-checksum="39359" --> |
| </p> |
| |
| <p class="c4">© Copyright <a href= |
| "http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2002. Distributed under the Boost Software License, |
| Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
| http://www.boost.org/LICENSE_1_0.txt)< |
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